On first impression this species may seem an unlikely natural vagrant to Western Europe and, instead, a more likely escape from captive collections. However, Chinese Pond Heron is kept rarely in captivity in Europe, and is a long distance migrant with extra-limital birds previously found both in continental Europe and North America. Thus the balance of evidence pointed very strongly towards the Kent record being a bird that originated from natural populations, and it was unanimously accepted to Category A.

Breeds in the Eastern Palearctic, from north-east India to north-east China and northern Japan, with populations migratory, moving south in winter to peninsular Thailand, Malaysia and Borneo.

It should be placed after Squacco Heron on the British List.

Slaty-backed GullLarus schistisagus
Adult or near-adult, Rainham, London, and Pitsea and Hanningfield, Essex,
13 January to 26 February 2011 (photographed).

The well-documented record established the identification of this individual. Provenance as a wild bird was not an issue as the species is not kept in captivity, and has been found in Europe before, as have a number of other north Pacific seabirds, including gulls, terns, auks and divers, demonstrating that vagrancy from this part of the world is possible. Thus it was straightforward to accept the species to Category A.

Breeds in the northern Pacific, in northern Japan, eastern Siberia and western Alaska, moving south in winter.

This record has now been placed in Category E following the initial circulation in 1993, and three subsequent reviews, in 1997, 2008 and 2016.

The record had already had three circulations before the occurrence of a wild bird in northern Italy in October 2011. On the basis of the Italian record, the British record was reviewed again this year.

For Category D records, BOURC procedures state a record can be reviewed up to three times in order to establish if the species should be transferred to either Category A or Category E of the British List. The 2016 circulation is the third and final review, and the species is now placed in Category E on the basis that four different memberships of BOURC (over 40 individual members) have been unable to come to a unanimous decision whether this bird originated from wild or captive sources.

The species is a plausible far-eastern Palearctic vagrant to Western Europe being a long distance migrant, and the first-winter age and late autumn occurrence on the English east coast during fall conditions were consistent with such an origin. However, the species (and age class) was imported to western Europe in the early 1990s for the avian bird trade; and subsequent to the ban in the trade of far eastern birds there have been no further British records. Thus the only British record coincided with the known import of the species into western Europe and so BOURC could not confidently determine the origin of the Humberside bird as likely to have been of natural occurrence.

Some observers may be surprised at the length of time and final decision for this record, but BOURC hopes that they will understand the thoroughness of our process.

It is also interesting to compare the initial expectations, and subsequent evidence and outcome for this species in relation to the British List with Chinese Pond Heron, described above.

These decisions will be published as part of the BOURC’s 46th report due to be published in IBIS in January 2017. Upon publication of these decisions, the British List will stand at 603 species (Category A = 585; Category B = 8; Category C = 10).